The field includes internal combustion engines. More particularly, the field includes opposed piston engines. More particularly still, the field includes opposed piston engines with a plurality of cylinders, or multi-cylinder opposed piston engines.
In an opposed piston engine, each cylinder has two ends and two pistons, with a piston disposed in each end. An inlet port is machined or formed in one end (“the inlet end”) of the cylinder, and an exhaust port in the other end (“the exhaust end”). An opposed piston engine may have one or more crankshafts and/or other outputs and may use a variety of fuels. In a typical opposed piston engine, an air-fuel mixture is compressed in the cylinder bore between the crowns of the pistons as they move toward each other. The heat resulting from compression causes combustion of the air-fuel mixture as the pistons near respective top dead center (TDC) positions in the middle of the cylinder. Expansion of gases produced by combustion drives the opposed pistons apart, toward respective bottom dead center (BDC) positions near the ports. Movements of the pistons are phased in order to control operations of the inlet and exhaust ports during compression and power strokes. Advantages of opposed piston engines include efficient scavenging, high thermal and mechanical efficiencies, simplified construction, and smooth operation. See The Doxford Seahorse Engine, J F Butler, et al., Trans. I. Mar. Eng., 1972, Vol. 84.
Recent technology designs described in the cross-referenced patent applications have improved many aspects of opposed piston engine construction and operation. For example, novel cooling designs focus on the thermal profiles exhibited by engine power components during engine operation. In this regard, tailored cooling effectively compensates for the longitudinally asymmetrical thermal signatures exhibited by cylinders during engine operation, while the opposed pistons are cooled by radially symmetrical application of coolant to the backs of their crowns. Cylinder construction is simplified by limiting cylinder liner length, which allows pistons to be substantially withdrawn and their skirts to be lubricated during engine operation. This design reduces welding and increases the power-to-weight ration of the engine. In order to reduce side forces on the pistons, no linkage pins (also called wristpins and gudgeon pins) are mounted within or upon the pistons.
Nevertheless, there is a need to integrate recent technological advances with additional improvements in multi-cylinder opposed piston engine constructions in order to further enhance the power-to-weight ratio, durability, adaptability, and compactness, and thereby increase the range of use, of such engines.